The invention concerns a method for the selective and self-aligned deposition of at least one metal layer on conductive regions on the surface of isolating or semiconductive substrates, and an apparatus for implementing the method.
Previously, methods of the above-mentioned kind could be implemented only on a wet chemical basis by electrolessly or electrolytically depositing a metal from the solution of one of its salts on regions made conductive or activated on the surface of an isolating substrate. Wet chemical processes, however, have the disadvantage that the substrates to be coated become contaminated, which may impair the function of the components to be manufactured and give rise to ecological problems when the baths used for coating are disposed of. Dry coating methods, such as cathode sputtering and vapor deposition, are primarily used to deposit metal layers on the entire surface of a substrate. Although these dry methods permit the selective deposition of metal on substrates with the aid of a metal mask whose openings correspond to the metal pattern to be deposited and which is positioned on or at a short distance from the substrate, such metal masks are relatively complicated to manufacture and their alignment relative to the substrate has to be very accurate. If the substrate, prior to the deposition of the metal, has to be subjected to steps in which its shrinkage is not fully controllable, as is the case, for instance, with ceramic or plastic substrates, then metal layers, whose structures correspond to the structures already existing on the substrate, can be selectively deposited only if the permissible manufacturing tolerances are very high. As the trend towards microminiaturization and thus to ever higher packing densities is increasing and the conductor widths are decreasing, such generous manufacturing tolerances are no longer practicable.